As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ROUTING COMPRESSION TEST FOUND NR 4 CYLINDER COMPRESSION LOW. REMOVED CYLINDER AND FOUND THE INTAKE VALVE SEAT HAD BEEN INSTALLED AND GROUND CROOKED AT THE FACTORY. SEAT REINSTALLED AND GROUND CORRECTLY AND REINSTALLED ON THE ENGINE.